1. Field of the Invention
The present invention relates to a hand tool having an adjustable head with a joint lock mechanism, especially a hand tool with a head of adjustable angles and easier, more secured positioning. The present application claims priority based on ROC (Taiwan) Patent Application No. 093213843.
2. Description of the Related Art
Conventional hand tools with an adjustable head, such as those disclosed in U.S. Pat. No. 6,216,567, comprise a head and a handle. The head has a convex portion which can be pivotally coupled to a concave portion of the handle by a screw. A joint lock mechanism comprises a toothed portion formed along the surface of the convex portion, a pin and a push button. The pin is received in a longitudinal hole having a shoulder portion and extending along the length of the handle. A toothed portion is formed at one end of the pin opposite to the toothed portion of the convex portion while the other end has an extended portion. A spring encircles the extended portion of the pin and abuts against a shoulder portion of the longitudinal hole at the other end to provide the pin with a forward force such that the toothed portion of the pin engages the toothed portion of the convex portion to lock and position the head of the wrench. The push button is received in a hole having a shoulder portion and being perpendicular to the longitudinal hole. One end of the push button abuts against a spring received in the shoulder portion of the hole and has an extended portion. One side of the extended portion of the push button is formed with a slot keeping in contact with the extended portion of the pin. The depth of the slot is gradually deepened towards the push button such that a gap is formed between the push button and the extended portion of the pin when the push button is pressed down. Therefore, the head of the wrench is rotatable with respect to the handle and pushes the pin such that the angle of the wrench can be adjusted. However, this kind of wrench cannot sustain high torque due to the configuration of the slots in the extended portion of the push button and the extended portion of the pin. In addition, since the extended portion of the pin is slidable with respect to the slot of the push button, it is not possible to lock the head effectively. Moreover, the extended portion of the push button and the extended portion of the pin may be worn out or fractured after use for a long period, which subsequently causes inconvenience when they are in use and reduces the life time of the wrench.
TW569860 has disclosed a wrench comprising a head and a handle. Again, the head has a convex portion which can be pivotally coupled to a concave portion of the handle by a screw. A toothed portion is formed along the surface of the convex portion to engage a ball received in a hole formed in the concave portion of the handle such that the head can be positioned at a certain angle. A push button is received in a hole formed radially in the handle and a spring is disposed in the bottom of the hole and abuts against the bottom end of the push button. A stepped groove is formed at the side of the push button such that a cap can be formed between the push button and the ball when the push button is pressed down and the head can push the ball and rotate with respect to the handle to adjust the angle of the wrench. Again, this kind of wrench cannot sustain high torque. In addition, since the teethed portion of the convex portion is of a sharp arc shape, it is likely that the teethed portion may be fractured due to high torque which renders the wrench unusable.
From the above, it is necessary for the industry to provide a hand tool having an adjustable head with a joint lock mechanism, which offers convenient and secured angle adjustment and positioning and can overcome the defects mentioned in the prior art.